An injection unit of the type described has become known from DE-A-33 29 705. In this patent, a die-casting machine is described, the injection piston of which being releasably connected with its associated piston rod by screws, thus providing a ram unit consisting of two parts between which pressure sensors have been interposed. The output signals of these pressure sensors, however, could only be used for measuring and indicating purposes, but not for a control, particularly not for the control of the transition from the filling phase to the squeezing phase. The reason is that with such an arrangement, the output signals of these pressure sensors can only indicate subsequently the fact that an event, e.g. the end of the filling phase, has happened at a certain moment and is terminated. Of course, for controlling purposes, a certain forecast is necessary and a time lag is needed for emitting and executing a corresponding control command. In the pertinent literature, it has already repeatedly been described what happens when the injection piston tries to move forward with full velocity at that moment in which the die or mold is fully filled up. This effect is often called "water hammer" which results in a slight opening of the two mold halves under the sudden high pressure known as the so-called "die-venting"), so that the molten metal gets into the, thus formed, interspace between the two mold halves. This leads to a bad quality of the product on account of flashes formed on it, or even to waste.